1. Field
The present invention relates to computer vision, more particularly to a video stabilizing method and a video stabilizing system for stabilizing videos with high-spatial-resolution using a dual-camera system, such as a static-active camera system or an active-active camera system.
2. Description of the Related Art
With the development of computer vision and the enhancement of worldwide attention on security, intelligent visual surveillance is now being paid more attention than ever before. And the related technology has been gradually applied for military and civilian purposes. In earlier applications, the intelligent degree is low. Therefore, security surveillance is mainly determined manually for the event occurred in the monitored videos with low degrees of reliability and automation. And it is mainly used for criminal evidence collection in visual surveillance. However, presently, intelligent visual surveillance pays more attention to criminal early warning to reduce occurrence of criminal cases.
In traditional surveillance, a single static camera has been unsuitable for modern surveillance requirement. Firstly, because the single static camera has a fixed viewpoint and when the moving target moves out of the viewing field, information of the monitored target will be completely lost. Secondly, due to the conflict between image resolution and the size of the viewing field, the viewing field will be relatively small if the required image resolution is high, especially for long-distance surveillance.
Therefore, a single active camera may be adopted to solve the conflict between the image resolution and the size or dimension of the viewing field. However, during the active tracking of the moving target, due to the continuous changes of the camera parameters, the background and the target in the image will move accordingly, so that it is very difficult to accurately predict the movement of the target. On the other hand, the camera can not be accurately controlled in addition to the difficult estimation of the camera movement time, so that the target may easily lost in the image or video whether an computer-controlled automatic tracking method or a manual tracking method is adopted. Therefore, robustness for capturing high-spatial-resolution video of a target by a single active camera is low.
Thus, video stabilization shall be performed to make the moving target in the video run more smoothly with improved visualization effect. In addition, after video stabilization, desired features may be easily extracted from the monitored target. Further, computer vision researches may be performed on the videos after video stabilizing, such as gesture recognition, behavior and gait analysis, or object identification.
In the case of long-distance surveillance, high-spatial-resolution frames of the interested targets captured may need to perform stabilization to increase video visualization effects. Generally, because there is a long distance between the target and the high-spatial-resolution camera, minor trembling of the camera may lead to severe changes of the moving targets in the image, thus the video visualization effect is inferior.
Further, for long-distance high-spatial-resolution surveillance, it is challenging to obtain a stabilized video with high-spatial-resolution, because there are problems such as image blurriness, and incompleteness in the acquired high-spatial-resolution video. The image blurriness is mainly caused by camera shaking, because the camera has to be operated in a high-speed mode to ensure the effective tracking of the active camera to the moving target, which may cause image blurriness in the video. In a prior dual-camera monitoring system, although a low-spatial-resolution camera is used for preventing the moving target from being lost, it is difficult to ensure each high-spatial-resolution frame to completely contain the moving target. Because each action of the active camera does need a certain time period for response which is hard to be accurately determined, thus there is always overtuning such as overshooting or undershooting due to the time delay in mechanical movement during controlling of the camera. Further, there may be a dithering region in the obtained video thereof. If the moving target runs at overspeed, there is an over-controlling frequency of the active camera which may result in inter-frame dithering.